Label printers are known, which use a supply of tape, housed in a cassette, received in the label printer. The tape comprises an image receiving layer and a backing layer which are secured to one another via an adhesive layer. Such label printers include a cutting mechanism for cutting off a portion of the tape after an image has been printed onto the image-receiving layer so that the portion of tape having the image can be used as a label. After the tape has been cut, the cut portion of the tape is pulled from the printer through a slit in the printer housing. The backing layer can then be removed allowing the image-receiving layer to be secured to an object using the adhesive layer.
Known label printers comprise a cassette-receiving bay in which a cassette is received for printing. A printhead is provided in the cassette-receiving bay for co-operating with the supply of tape to print thereon. A platen may also be provided in the cassette-receiving bay positioned at a side of the tape opposite to the printhead when the cassette is received in the cassette-receiving bay. During printing, the printhead co-operates with the platen, with the tape passing therebetween for printing thereon. The platen may be driven by a motor for propagating the tape during printing. Alternatively, the platen may be freely rotatable and an additional drive roller may be provided for driving the tape during printing.
In an alternative arrangement to that described above, a platen may be provided within the cassette. In such an arrangement, the tape cooperates with a surface of the platen. When received in the cassette-receiving bay the platen in the cassette co-operates with a drive mechanism in the cassette-receiving bay for driving the tape during printing. Alternatively, the platen is freely rotatable and an additional drive roller may be provided for driving the tape. During printing, the printhead in the cassette-receiving bay co-operates with the platen in the cassette with tape passing therebetween for printing thereon.
In one arrangement, the printhead is moveable between a non-printing position and a printing position. In an alternative arrangement, the platen is moveable between a non-printing position and a printing position. In yet another arrangement, both the platen and printhead are movable so as to have non-printing and printing positions.
The tape may be of a direct thermal type on which printing is achieved by direct application of heat from printing elements on the printhead. Alternatively, an ink ribbon may be provided, whereby ink is transferred from the ribbon to an image receiving tape by application of heat to the ink ribbon via printing elements on the printhead. The cassette may include a roll of die cut labels rather than a continuous tape.
A problem exists in all the above-described arrangements, in that for good quality printing the tape and/or ink ribbon must be correctly aligned with the printhead during printing. Furthermore, the tape must remain correctly aligned with the printhead while printing occurs and must smoothly pass the printhead so as to ensure good quality printing. In order to ensure that this is the case, it is advantageous to prevent the cassette from moving during printing and cutting. Furthermore, the position of the cassette within the cassette-receiving bay should be predefined and readily reproducible whenever a cassette is inserted in the cassette-receiving bay.
The problem is exacerbated in hand held printers which may be moved around during printing. In such an apparatus, it is even more important that the cassette is locked in a fixed position during printing.
WO 2006/013466 (DYMO) discloses a cassette locking and ejecting arrangement for a label printer apparatus. A label printer comprising a cassette-receiving bay in which a tape cassette is inserted, is provided. The cassette receiving bay is provided with a plurality of spring-loaded ejecting members for ejecting a cassette from the cassette-receiving bay. When a cassette is inserted in the cassette receiving bay, a pair of locking members hold the cassette in place against the biasing force exerted by the ejecting members. To eject the cassette, the locking members are disengaged from the cassette allowing the cassette to be pushed out of the cassette-receiving bay by the force exerted by the ejecting members.
There is a problem with the above-described arrangement, that when a cassette is inserted into the cassette receiving bay by a user, it is possible that the cassette will not properly engage with all of the locking members. This may occur, for example, if a user presses on only one edge of the cassette during insertion. If a cassette is engaged with one, but not all, of the locking members, then although the cassette may be retained within the cassette receiving bay against the biasing force of the ejecting members, the cassette may not be aligned properly with respect to the platen and print head for printing.
WO 2006/013466 (DYMO) has a pair of locking members which are biased, by means of a spring, towards a locking position so as to lock a cassette inserted into the cassette receiving bay in place. However, in the event that the label printer apparatus is subjected to a sudden impact, i.e. if it is dropped by a user, it is possible that the locking members will be moved against the biasing force of the spring so as to release the cassette. Accordingly, when a user subsequently resumes printing with the label printer apparatus, the cassette will not be properly locked in the cassette receiving bay in the correct position for printing, and printing will be adversely effected or impossible.
Furthermore, in the case that a cassette inserted into a cassette receiving bay is not properly engaged by one or more of a plurality of locking members, it may not be apparent to a user, which locking members are not engaged properly with the cassette and what action is required in order to rectify the problem.